These studies aim to assess the role of cell cycle proteins in HIV neuropathogenesis. We will focus on the activation of the key CDK/RWE2F-1 pathway in cultured neurons to identify target genes potentially involved in HIV-induced neurodegeneration. The expression of such apoptotic targets will be then analyzed in brain tissue samples from HIV demented and non-demented patients to establish their relevance in vivo. Experiments have been designed to gather fundamental information related to the coupling of chemokine receptors to neuronal cell cycle proteins, and to determine the effect of HIV envelope proteins on the Rb/E2F pathway. Aim 1 will dissect the mechanisms implicated in the regulation of Rb and E2F-1 by the chemokine receptor CXCR4 in neuronal cultures and will evaluate the contribution of non-neuronal cells to the effect of SDF-1 on neurons. Aim 2 will focus on the effect of gp120s of different nature/structure on Rb and the pathways that controls the activity of p53 and E2F-1. Aim 3 will concentrate on the expression of E2F-specific targets in tissue samples from HIV-infected patients and will determine the role of cell cycle protein alterations in neuronal degeneration. To address these issues, a well-defined primary culture system, in which pure populations of rat central neurons can be examined both in the presence and in the absence of non-neuronal cells, will be used to discern direct effects of chemokines on neurons from indirect effects mediated by the glia and other non-neuronal cells. Then, human neurons and glia will be used, to confirm the most relevant observations in a human in vitro model. Finally, examination of brain tissue samples from HIV-infected patients with and without HAD, will be included to determine the relevance of our in vitro findings to the human pathology. The effects of chemokines, namely SDF-1, and HIV envelope proteins on the expression and activity of cell cycle components involved in apoptosis and differentiation will be investigated by a multidisciplinary approach including proteomics, pharmacology, molecular biology, and novel imaging/fluorescence methods. The proposed experiments will provide novel information on the roles of chemokines and neuronal-glia interactions in the context of the neurological complications of AIDS. The proteomic approach will help us recognize differential protein profiles associated with HIV neuropathogenesis, which may lead to the identification of novel disease biomarkers.